Double gate valve for passing material from a pressurized side of a bulkhead

ABSTRACT

A device for passing material from the pressurized side of a bulkhead in a tunnelling machine. The device comprises a double gate valve having a first gate opening in an upward direction and a second (downstream) gate opening in a downward direction. The bottom of the valve body carries for the first gate a seal backed by a pressurized chamber from which liquid leaks past the seal and into the body portion of the valve. This discourages ingress of spoil into the seal.

United States Patent Biggart Oct. 28, 1975 DOUBLE GATE VALVE FOR PASSING 2,742,193 4/1956 Thieme 222/148 MATERIAL FROM A pussumzsn sum 3 333133: 31:35; g g g g OOl'l 5 OF A BULKHEAD 3,765,576 10/1973 Ramsdale 222/148 X 7 l t l 1 or 2552:; mm Chlslehurst FOREIGN PATENTS OR APPLICATIONS 532,553 11 1956 C d 222 450 [73] Assignee: National Research Development and a Corporatlon London England Primary ExaminerDrayton E. Hoffman [22] Filed: Oct. 9, 1973 Assistant ExaminerCharles A. Marmor [211 pp No: 404,183 Agent, or F1rmCushman, Darby &

[30] Foreign Application Priority Data 57 ABSTRACT Oct. 13, 1972 United Kingdom 47380/72 A device for p g material from the pressurized side of a bulkhead in a tunnelling machine. The device S 222/148 222/ comprises a double gate valve having a first gate opening in an upward direction and a Second (down [58] new of "5531ig gg q gggi f ibg g stream) gate opening in a downward direction. The l bottom of the valve body carries for the first gate a seal backed by a pressurized chamber from which liq- [56] References Cited uid leaks past the seal and into the body portion of the UNITED STATES PATENTS valve. This discourages ingress of spoil into the seal. 1,313,491 8/1919 Lazzell 222/450 X 7 Cl 3 Dr F. 1,639,517 8/1927 Lassen 222/450 x awng gums US. Patent Oct. 28, 1975 Sheet 1 of3 3,915,347

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U.S. Patent Oct. 28, 1975 Sheet 2 of3 3,915,347

n 1/4 I I i m I A II DOUBLE GATE VALVE FOR PASSING MATERIAL FROM A PRESSURIZED SIDE OF A BULKHEAD This invention relates to apparatus for tunnelling generally horizontally, or on an incline, through ground which is capable of being excavated by mechanical digging or cutting mechanisms.

British Pat. Specification '1083322 describes one such tunnelling apparatus comprising a tunnelling shield including'a transverse pressure bulkhead, a power-driven rotary mechanical digging mechanism in a working chamber in front of the bulkhead, means for supplying a liquid suspension under pressure to the working chamber, and means for continuously removing spoil with a proportion of the liquid suspension from the working chamber.

The liquid used in operation of the device is preferably a thixotropic suspension, i.e. a suspension having a relatively high viscosity at low stress but a decreased viscosity when an increased stress is applied. Thus the suspension will initially be relatively free-flowing and can be pumped in this condition into the working chamber at the front of the shield. However, when it reaches or partly penetrates into the working face, the suspension is no longer moving and so it becomes substantially solid, or semi-solid, or viscous, and will thus materially assist in supporting the face,'or in forming in effect a pressure membrane on or in the ground, against which the pressure of the liquid suspension in the working chamber acts.

In the interests of economy, the tunnelling apparatus above described preferably includes means for separating spoil from the extracted material and for recirculating the remainder, which should ideally consist only of the thixotropic suspension, back to the working chamher.

It is an object of the present invention to provide a device for passing material from the pressurized side of a bulkhead in such an apparatus.

According to the present invention, this device may be provided by a double gate valve having an upwardly closing first gate followed by the second gate of the valve, and means for controllably venting to atmosphere that part of the valve body containing the seat for the first gate.

Preferably a seal between the bottom part of the valve body and the first gate is backed by a chamber adapted to be pressurized with a flow of substantially spoil-free thixotropic material whereby any leak past the seal is in an upwards direction to discourage the ingress into the seal of spoil present in the'extracted material.

That part of the valve body located between the two gates is preferably provided with an inlet port for a flow of the thixotropic material into said port and according to a preferred feature the cross section presented to said part by the inlet port is greater than that presented there by the venting means.

The second gate preferably closes in a downwards direction.

The invention also includes a tunnelling machine in- FIG. 1 shows a diagrammatic view of a tunnelling machine embodying the double gate valve of the present invention; and

FIG. 2 shows, on a larger scale than FIG. 1, a vertical section through the double gate valve;

FIG. 3 shows, on the same scale as FIG. 2, a vertical section through an alternative design of double gate valve according to the present invention.

Referring first to FIG. 1, a tunnelling machine 10 includes a transverse pressure bulkhead 14. A working chamber 16 between the bulkhead and the front of the shield contains a power driven rotary mechanical digging mechanism in the form of a cutter head 18. A thixotropic liquid suspension of sodium based bentonite slurry (5% byweight of bentonite in water) is supplied to chamber 16 at a rate of about 300 gallons per minute by a pump 20 so that in operation the cutter head revolves in a sealed chamber filled with bentonite slurry under pressure. Sodium based bentonite is, for example, available in Great Britain from Laporte Industries (under the trade name Fulbent) and from Berk Limited (under the trade name Berkbent). The pressurized bentonite forms a skin or filter cake on the excavated tunnel wall 21, the slurry penetrating the wall face to stabilize and seal it.

A chute 22 guides spoil-contaminated slurry from chamber 16 through an extractor (comprising a double gate valve 23) and into a wet sump 24 where any cobbles of over 100 mm are sifted out. The double gate valve which meters the discharge from the chute is shown in more detail in FIG. 2. The spoil-contaminated slurryis then pumped by pump 26 (FIG. 1) ma vibrating screen separator 28 (which removes particles larger than 6 mm) and then to four cyclones 29 which remove sand particles larger than micrometers. The sand removed is collected in tank 30 and the clean bentonite slurry leftis discharged from the cyclones into tank 32 for temporary storage. From tank 32, the clean bentonite slurry is delivered to the tunnel by pump 34 and divided between the wet sump (via pipe'36), the working chamber (via pump 20), and the extractor 23 (via pipe 38). A pressure control valve 40 allows the controlled removal of slurry and sand from the chamber and also allows any air which may be entrained in chamber 16 to escape.

In operation of the apparatus shown in FIG. 1, the various pumps are started to give the necessary bentonite slurry flows through the system and the rotary cutting head is driven to cut away the ground in front of the tunnelling machine which is pushed forward, as the ground is cut away, by a ring of hydraulic jacks (not shown) acting between a bulkhead (not shown) at the rear of the machine and the last ring of the tunnel lining 42. When the machine has progressed by a sufficient amount, the cutter and the bentonite slurry flows are stopped and some of the hydraulic jacks are retracted towards the tunnelling machine 10. This allows the next ring of the lining to be built and grouted into place within the tail of the machine whereupon the jacks are again extended and the sequence of steps above described is repeated.

The present invention lies in the double gate valve which is used as the extractor and the illustrated embodiment of this valve shown in FIG. 2 has an upwardly closing first gate 52 followed by the second gate 54 which closes downwardly. The valve body 56 has an inlet 58 for the introduction of spoil-contaminated bentonite slurry from work chamber 16 of the tunnelling machine, and an outlet 60 for the discharge of material from the valve body central part (62) located between the gates 52 and 54. Guides 63, 64 guide the motion of the two gates. The inclination of the bottom part (65) of the valve body is substantially equal to the angle of repose of the spoil particles in the slurry leaving the working chamber.

At its upper end, gate 52 is arranged to engage with a rubber seat 66 located at the top of the valve body above the level of an outlet port 68. Port 68 vents the upper part of the valve body to atmosphere via a pipe 100 controlled by a conventional hand wheel operated gate valve 104. A pressure gauge 102 indicates the pressure in pipe 100 on the upstream side of valve 104. The gate 52 is sealed at the bottom of the valve body by two sets 69, 70 of lip seals mounted in a block 72. A cavity 74 in the block is connected through inlet port 76 with the pipe 38 shown in FIG. 1, and an outlet 76' (behind port 76 as viewed in FIG. 2) from the cavity is connected by an appropriate pipe 400 (shown diagrammatically in FIG. 2) with an inlet port 78 into the body part 62. Pipe 400 is provided with a throttling valve 402 designed to maintain the bentonite in chamber 74 at a positive pressure relative to the bentonite on the upstream side of gate 52. A baffle 80 sprays out the bentonite entering through port 78.

In operation of the system shown in FIG. 1, the discharge of material from chute 22 is fed into the valve body 56 (FIG. 2) through inlet port 58 with gates 52 and 54 closed. The central part 62 of the valve body is full of clean bentonite slurry up to or slightly above the level of outlet port 68 and pockets of air under pressure are trapped in the top of the valve body by the bentonite slurry present on both sides of gate 52. To operate valve 23, a flow of bentonite slurry is started through inlet ports 76 and 78, gate 52 is moved down into the open position illustrated for the gate in FIG. 2. Due to the slope chosen for valve bottom 65, a certain quantity of particulate spoil material in the first part of the valve body flows quickly into the central part 62 and when this flow has finished gate 52 is closed and, gate 54 is moved upwards into the open position shown for the gate in FIG. 2. For the reason already mentioned above, not only the bentonite slurry but also the particulate material in the bentonite slurry flow quickly past raised gate 54 and through outlet 60 to the wet sump 24 (FIG. 1). The continuing flow of bentonite slurry from port 78 quickly flushes part 62 (FIG. 2) of any spoil particles remaining there. Gate 54 is then closed and bentonite slurry continues to be pumped into part 62. As the bentonite level rises in part 62, air is expelled through port 68 and pipe 100 to atmosphere. When the bentonite reaches the level of port 68, it will begin to pressurize the pocket of air now trapped by the bentonite and the bentonite level will continue to rise until the pressure of the trapped air prevents any further increase in the bentonite level. The pressure of the trapped air at which this happens will depend upon the throttling effect of valve 104 and this valve is manually set so that the trapped air pressure reaches a value about equal to that in the working chamber. of the tunnelling machine. When the bentonite level can no longer rise in part 62 because of the air pressure, bentonite will begin to pass along pipe 100 which discharges into wet sump 24 shown in FIG' 1.

During the period (4 to 5 seconds, say) from when gate 54 is closed and the bentonite is seen to be flowing from pipe into sump 24, the corresponding flow through inlet 76 clears the upper lip seal 69 of any grit which may have entered from the slurry and any spoil which has penetrated to cavity 74 is swept away through the cavitys outlet port, this flow (like that through pipe 78) being continuous throughout the operation of the double gate valve. It will be appreciated that every time gate 52 is opened the previously separated air pockets join up so that the upper part of the valve body is occupied by a single pocket of air. This means that seat 66 is at all times surrounded by air and there is no possibility of slurry spoil preventing satisfactory seating there.

In an alternative embodiment shown in FIG. 3, the double gate valve of FIG. 2 is modified so that the seat 66 for the first gate is surrounded by clean bentonite slurry instead of air. Accordingly, port 68, pipe 100 and baffle 80, are replaced by an overflow pipe 200. This pipe communicates via the top plate of valve body 56, with the space between gates 52 and 54 and it discharges into wet sump 24. The remainder of the double gate valve is identical with that already described above with reference to FIG. 2, except for an extension chamber 300 situated on the upstream side of gate 52. Extension chamber 300 is arranged to'hold any pocket of air accumulating on the upstream side of gate 52 in operation of the double gate valve. This ensures that the bentonite level on the upstream side of gate 52 will at all times be above the level of seat 66. A manually operated valve 302 allows the air to be exhausted to atmosphere every so often so that the bentonite is not depressed to a level below seat 66 by increasing air pressure.

The operation of this embodiment is identical with that described with reference to the FIG. 2 embodiment except that now gate 52 seats in a bentonite surrounding rather than in an air surrounding. As before completion of the filling operation when both gates are closed, is accompanied by a visable flow of bentonite from the outlet end of overflow pipe 200 into wet sump 24.

Corresponding parts in the two embodiments have been identified by the same numerals throughout.

It will be appreciated from the above discussion of the operation of the embodiments of FIGS. 2 and 3 that these Figures do not show the double gate valve in an operative position because, in practice, one or both of gates 52, 54 will be closed at any particular instant. FIGS. 2 and 3 on the other hand show both these gates to be open in order more clearly to illustrate the various components of the valve.

Both the embodiments described in the specification can be operated if desired by arranging for cavity 74 to be flushed with a continuous flow of water instead of bentonite.

I claim:

1. A device for passing material from the pressurized side of a bulkhead, the device comprising a double gate valve having a body portion, a first gate at the inlet side of said body portion, a first seat onto which the first gate closes in a generally upwards direction, a second gate at the outlet side of said body portion, a seat for said second gate, guide means for said first and second gates constraining said gates to slide in their respective planes when moving between their open and closed positions, and means for maintaining said seat for said first gate free of said material passing through said device, said means including valve means for controllably venting to atmosphere that part of the valve body containing the seat for the first gate.

2. A device as claimed in claim 1 including a seal between the bottom part of the valve body and the first gate, a backing chamber backing said seal, means permitting pressurization of said backing chamber with a flow of substantially spoil-free liquid, and means permitting a leak of said liquid past said seal and into the valve body thereby to discourage the ingress into the seal of spoil present in the extracted material.

3. A device as claimed in claim 2 in which the spoilfree liquid is a thixotropic material.

4. A device as claimed in claim 1 including an inlet port located in that part of the body portion located between the two gates, said inlet port permitting a flow of substantially clean thixotropic material into said part.

5. A device as claimed in claim 1 including venting means for controllably venting to atmosphere that part of the valve body containing the seat for the first gate and an inlet port located in said part permitting a flow of substantially clean thixotropic material into said part, the internal cross-section presented to said part by the inlet port being greater than that presented there by said venting means.

6. A device as claimed in claim 1 in which the second gate closes against its seat in a generally downwards direction.

7. A double gate valve for passing a material in a slurry from the pressurized side of a bulkhead, the valve comprising a body,

a first gate at the inlet side of said body,

a first seat onto which the first gate closes in a generally upward direction,

a second gate at the outlet side of said body,

a seat for said second gate,

guide means for said first and second gates constraining said gates to slide in their respective planes when moving between their open and closed positions, and

means for maintaining said slurry away from said first seat, said means including valve means for controllably venting to atmosphere that part of the valve body containing the seat for said first gate. 

1. A device for passing material from the pressurized side of a bulkhead, the device comprising a double gate valve having a body portion, a first gate at the inlet side of said body portion, a first seat onto which the first gate closes in a generally upwards direction, a second gate at the outlet side of said body portion, a seat for said second gate, guide means for said first and second gates constraining said gates to slide in their respective planes when moving between their open and closed positions, and means for maintaining said seat for said first gate free of said material passing through said device, said means including valve means for controllably venting to atmosphere that part of the valve body containing the seat for the first gate.
 2. A device as claimed in claim 1 including a seal between the bottom part of the valve body and the first gate, a backing chamber backing said seal, means permitting pressurization of said backing chamber with a flow of substantially spoil-free liquid, and means permitting a leak of said liquid past said seal and into the valve body thereby to discourage the ingress into the seal of spoil present in the extracted material.
 3. A device as claimed in claim 2 in which the spoil-free liquid is a thixotropic material.
 4. A device as claimed in claim 1 including an inlet port located in that part of the body portion located between the two gates, said inlet port permitting a flow of substantially clean thixotropic material into said part.
 5. A device as claimed in claim 1 including venting means for controllably venting to atmosphere that part of the valve body containing the seat for the first gate and an inlet port located in said part permitting a flow of substantiaLly clean thixotropic material into said part, the internal cross-section presented to said part by the inlet port being greater than that presented there by said venting means.
 6. A device as claimed in claim 1 in which the second gate closes against its seat in a generally downwards direction.
 7. A double gate valve for passing a material in a slurry from the pressurized side of a bulkhead, the valve comprising a body, a first gate at the inlet side of said body, a first seat onto which the first gate closes in a generally upward direction, a second gate at the outlet side of said body, a seat for said second gate, guide means for said first and second gates constraining said gates to slide in their respective planes when moving between their open and closed positions, and means for maintaining said slurry away from said first seat, said means including valve means for controllably venting to atmosphere that part of the valve body containing the seat for said first gate. 